Evaluation of Standard Right-of-Way Fence Post Anchors

64 Pages·2003·2.88 MB·English

by  Patrick Szary

FHWA NJ 2000-07

Evaluation of Standard Right-of-Way Fence Post
Anchors Versus Drive Anchors

FINAL REPORT
February 2001

Submitted
by

Mr. Patrick Szary

Research Engineer and Associate Director

Mr. Judson Wible Dr. Ali Maher
Graduate Research Assistant Professor and Chairman

Dept. of Civil & Enviro nmental Engineering
Center for Advanced Infrastruc ture & Transportation (CAIT)
Rutgers, The S tate University
Piscataway, N J 08854-8014

NJDOT Research Project Manager
Mr. Raj Chawla

In cooperation with

New Jersey

Department of Transportation
Division of Research and Technology
and
U.S. Department of Transportation
Federal Highway Administration
Disclaimer Statement

"The contents of this report reflect the views of the
author(s) who is (are) responsible for the facts and the
accuracy of the data presented herein. The contents do
not necessarily reflect the official views or policies of the
New Jersey Department of Transportation or the Federal
Highway Administration. This report does not constitute
a standard, specification, or regulation."

The contents of this report reflect the views of the authors,
who are responsible for the facts and the accuracy of the
information presented herein. This document is disseminated
under the sponsorship of the Department of Transportation,
University Transportation Centers Program, in the interest of
information exchange. The U.S. Government assumes no
liability for the contents or use thereof.
TECHNICAL REPORT STANDARD TITLE
1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No.
FHWA 2000-07
4. Title and Subtitle 5. Report Date
Evaluation of Standard Right-of-Way Fence Post Anchors Versus February 2001
Drive Anchors 6. Performing Organization Code
CAIT/Rutgers
7. Author(s) Mr. Patrick Szary, Mr. Judson Wible, and 8. Performing Organization Report
NFoH.W A 2000-07
Dr. Ali Maher
9. Performing Organization Name and 10. Work Unit No.
Address
New Jersey Department of Transportation
CN 600 11. Contract or Grant No.

Trenton, NJ 08625
13. Type of Report and Period Covered
12. Sponsoring Agency Name and Final Report
FAeddderersasl Highway Administration 6/27/1997 - 3/31/1999
U.S. Department of Transportation
Washington, D.C. 14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract
Right-of-way fence installation has not received a great deal of attention in literature during
past years, because traditionally common construction practice used concrete for the
fencing footings.1 In hard to access areas like wetlands, steep roadway cuts, and wooded
terrain commonly associated with locations that need right-of-way fencing, alternative
simple system footings are sometimes used. Recent roadside field installations have
demonstrated a potential for satisfactory performance of the simple systems. The main
objective of this research is to compare the viability of these simple systems to concrete
foundations. Field testing was conducted to evaluate the deflection performance of the
posts installed in “concrete” versus “drive anchors.” A static load was applied to each post
system at two feet above grade. Also, an FEM analysis was conducted to simulate actual
site testing conditions. Based on this research, the drive anchors and the concrete
systems both performed within tolerable limits established in this study. It was also
determined that in areas where only manual means of installation could be used there was
a significant cost savings in favor of the drive anchors. In summary, the results indicate that
the drive anchor and the concrete systems can be used interchangeably.

17. Key Words 18. Distribution Statement
right of way, drive anchor, concrete, footing,
fence post, fencing,
19. Security Classif (of this report) 20. Security Classif. (of this 21. No of 22. Price
Unclassified Unclassified 64
Form DOT F 1700.7 (8-69)
Acknowledgements

The authors wish to express their appreciation to the New Jersey Department of
Transportation for the allotment of funds making this research possible. Special thanks are
extended to Mr. Raj Chawla and Mr. Frank Palise of the NJDOT for their support and
extending the opportunity to participate in such a significant and extensive research program.
The authors would also like to thank Dr. Gary R. Consolazio and Jae H. Chung of the Univ. of
Florida, Dept. of Civil Engineering for their efforts on the Finite Element Modeling and
Analysis of Fence Post Anchorage Systems portion of this report.

ii
TABLE OF CONTENTS
Page
Abstract...................................................................................................................................1
Introduction..............................................................................................................................1
Mechanisms of Failure........................................................................................................3
Comparison.........................................................................................................................3
NJDOT Approved Fence Contractors.................................................................................5
Post Type............................................................................................................................7
End, Corner, and Pull Posts............................................................................................7
Line Posts........................................................................................................................7
Breaking Loads of Fence Fabric.........................................................................................8
Experiment..............................................................................................................................9
Background for Pullouts......................................................................................................9
Finite Element Modeling......................................................................................................9
Site Selection.....................................................................................................................10
Installation of Fence Posts................................................................................................12
Post Pull-out Set-up..........................................................................................................15
Testing...............................................................................................................................17
Data and Analysis.................................................................................................................18
Field Testing Results.........................................................................................................18
Analysis of 2.5 inch diameter posts..................................................................................19
Analysis of 3 inch diameter posts.....................................................................................21
Yielding verification in concrete footing.............................................................................24
Material and Labor Costs..................................................................................................24
FEM Verification of Results...................................................................................................27
Conclusions..........................................................................................................................29
Appendix 1 Finite Element Modeling and Analysis of Post Anchorage Systems.................31
Introduction........................................................................................................................31
Analysis Software Chosen................................................................................................32
Constitutive Models for Materials.......................................................................................33
Analysis Models.................................................................................................................36
Dimensions of the Steel Post........................................................................................36
Model I : Concrete Footing System..............................................................................36
Model II : Steel anchor System......................................................................................39
Results..............................................................................................................................43
Conclusion.........................................................................................................................47
Appendix 2 Department of Transportation Specifications....................................................48
Pennsylvania Department of Transportation Research....................................................48
Description of PENNDOT Testing....................................................................................48
Explanation and Summation of PennDOT Testing Results.............................................49
Conclusions and Recommendations of PENNDOT.........................................................49
Other Department of Transportation Specifications.........................................................50
Appendix 3 Raw Data for Post Pull-outs...............................................................................55
iii
LIST OF FIGURES
Figure 1 Diagram of an anchor shoe with two sets (four “L” angle-shaped beams) of
anchor blades....................................................................................................................2
Figure 2 A typical section of two types of fence post systems.................................................3
Figure 3 Satisfaction of NJDOT approved fence contractors with drive anchors....................6
Figure 4 NJDOT approved fence contractors preferred use of drive anchors or
concrete.6..........................................................................................................................6
Figure 5 Diagram showing different positions and alignments of a fence post
installation..........................................................................................................................7
Figure 6 Soil gradation analysis for site location.....................................................................11
Figure 7 First hole dug on-site for a 2.5 inch line post set in a concrete footing....................12
Figure 8 A diagram of the hole locations, indicating size of post, anchor mechanism,
and identification number................................................................................................13
Figure 9 Photograph of driven 2.5 inch line post with one set of anchor blades
positioned for installation.................................................................................................14
Figure 10 Photograph of driven 2.5 inch line post with one of the anchor blades driven
via a sledgehammer into position....................................................................................14
Figure 11 Photograph of fully installed 2.5 inch line post and anchor blades ready to
be tested..........................................................................................................................15
Figure 12 The testing apparatus consisting of a ratchet mechanism, load cell, and
bulldozer are shown........................................................................................................15
Figure 13 The data acquisition unit. The monitor shows the graphical representation
of the ratchet loading.......................................................................................................16
Figure 14 The deflectometer was attached to a stationary pole that was driven in the
ground nearby so the deflection could be measured at the pull height...........................17
Figure 15 The pull-out system is shown just after beginning a pull-out test...........................17
Figure 16 This figure shows a before and after picture of the ratchet and load cell.
The before picture, on the left, shows the devices lying on the crates ready for
testing, the after picture shows the system in tension....................................................18
Figure 17 Testing results Anchor Post #2 of a 2.5 inch diameter line post installed
with drive anchors. Shows deformation of the soil resulting in post inclination..............20
Figure 18 The Deflection versus loading of the 2.5 inch diameter fence posts.....................21
Figure 19 Testing results of Anchor Post #6 a 3 inch diameter post installed with drive
anchors. Shows deformation of soil resulting in post inclination....................................21
Figure 20 Testing results of Anchor Post #5 a 3 inch diameter post installed with
concrete. Shows the formation of a plastic hinge in the post.........................................22
Figure 21 Deflection versus loading of the 3 inch diameter posts, a comparison
between a concrete footing and anchor posts................................................................23
Figure 22 The deflection versus loading comparison of 3 inch versus 2.5 inch
diameter concrete posts.................................................................................................24
Figure 23 Material cost breakdown for fence post installations..............................................26
Figure 24 Total net material cost for fence post installations.................................................26
Figure 25 Comparison of projected FEM deflections to the actual experimental
deflections for a 2.5 inch post.........................................................................................28
Figure 26 Comparison of projected FEM deflections to the actual experimental
deflections for a 3 inch post............................................................................................28
Figure 27 Post Systems.........................................................................................................31
Figure 28 Physical Dimensions of Concrete Footing System................................................37
iv
Figure 29 Concrete Footing FEA Model..................................................................................38
Figure 30 Concrete Footing FEA Model Details......................................................................39
Figure 31 Physical Dimensions of Steel anchor Footing System..........................................40
Figure 32 Overall Steel Anchor FEA Model.............................................................................41
Figure 33 Central Core of Soil Immediately Adjacent to Steel Anchors.................................41
Figure 34 Details of Soil Slices and Soil Wedges Near the Steel Angle Anchors..................42
Figure 35 Deformed Shape and Plastic Strains for Footing System (Expanding Zone
of Plastic Strains in Steel Post Indicates Formation of a Plastic Hinge)........................44
Figure 36 Deformed Shape and Plastic Strains for Anchor System (Expanding Zone
of Plastic Strains in Steel Post Indicates Formation of a Plastic Hinge)........................45
Figure 37 Load-Displacement Curves for the two Post Systems Analyzed.........................46

v
LIST OF TABLES
Table 1 Drive Anchors versus Concrete Footings , 3..............................................................4
Table 2 Summary of NJDOT approved contractors 6............................................................5
Table 3 ASTM post recommendations...................................................................................8
Table 4 Fence fabric breaking loads.......................................................................................9
Table 5 Breakdown of material costs for fence post installations........................................25
Table 6 Soil model parameters.............................................................................................34
Table 7 Parameters for the LS-DYNA3D concrete model....................................................35
Table 8 Post dimension parameters.....................................................................................36
Table 9 Model computational size.........................................................................................40
Table 10 Results of PENNDOT testing................................................................................48
Table 11 Minimum section modulus about major and minor axis........................................53
Table 12 Minimum section modulus about major axis.........................................................53
Table 13 Results from 2.5 inch diameter post pull-outs.......................................................55
Table 14 Results from 3 inch diameter post pull-outs..........................................................55
vi
ABSTRACT
Right-of-way fence installation has not received a great deal of attention in literature during
past years, because traditionally common construction practice used concrete for the
fencing footings.1 In hard to access areas like wetlands, steep roadway cuts, and wooded
terrain commonly associated with locations that need right-of-way fencing, alternative simple
system footings are sometimes used. Recent roadside field installations have
demonstrated a potential for satisfactory performance of the simple systems. The main
objective of this research is to compare the viability of these simple systems to concrete
foundations.

Field testing was conducted to evaluate the deflection performance of the posts installed in
“concrete” versus “drive anchors.” A static load was applied to each post system at two feet
above grade. Also, an FEM analysis was conducted to simulate actual site testing
conditions.

Based on this research, the drive anchors and the concrete systems both performed within
tolerable limits established in this study. It was also determined that in areas where only
manual means of installation could be used there was a significant cost savings in favor of
the drive anchors. In summary, the results indicate that the drive anchor and the concrete
systems can be used interchangeably.

INTRODUCTION
The failure of a right-of-way fence post is both dangerous and unsightly. Public safety
concerns that are posed by a failed post and fabric present the need for quick and
inexpensive replacement. Current remedial procedures require considerable labor time and
maintenance funds to remove and replace the damaged posts. This study will determine
whether fence post installation crews should continue with current installation procedures or,
based on economic, time, and performance factors, change to the anchor post method.

A concrete fence footing system is comprised of a uniform hole with a post set in a vertical
position, and then backfilled with concrete. Depending on the materials used, the initial
curing time can take up to several days. Fence fabric cannot be stretched, thus burdening
the fence post, until the concrete has set. The necessary time delay, to allow the concrete to
reach sufficient strength to withstand loading, accounts for part of the disruption and difficulty
in working with concrete footing systems. Replacement is another dilemma with the
concrete system. Replacement procedures require removing the fence post by either
cutting the post at its base or by removing the post and footing, digging a new hole usually
right next to the old hole, and then re-setting the new post in concrete. Since these
installations are along the right-of-way, workspace is limited, and in addition, the new post
must be set very close to the previous one that is being removed. This procedure is both
time and labor intensive.

An anchor footing system is comprised of a fence post driven into the ground and an
accompanying anchor system. The anchor blades, which are part of the anchor system,
1
are “L” angle-shaped beams roughly 30 inches long and about 1.5 inches wide with a
thickness of 0.25 inches. The anchor blades are secured to the post by a shoe. The shoe is
a dual-screw clamp with slotted openings on its sides, as shown in Figure 1. During
installation, the shoe is placed around the post and the screws are tightened on both sides of
the shoe, thus clamping it securely in place. In a typical installation the shoe is positioned
such that when the anchor blades are driven they will be completely below the ground
surface. After the shoe is secured the anchor blades are inserted and aligned in the slots.
The blades are then driven into the soil at a downward 45-degree angle through the slots in
the shoe, as shown in Figure 2, thus creating a rigid connection between the anchors blades
and the post.

Figure 1 Diagram of an anchor shoe with two sets (four “L” angle-shaped beams) of anchor
blades.2

2